1. Field of the Invention
The present invention relates to a two-stage brake device of a tape measure, which has simple components and fixes the tape at a desired extending length by means of the elasticity of the components so as to effectively control and locate the tape by two stages and ensure safe use thereof.
2. Brief Description of the Prior Art
A conventional tape measure includes a housing, a reel disposed in the housing and a tape elastically extensibly wound on-the reel by a coil spring. A user can linearly pull the tape out of the housing through an opening thereof for measuring a length or retract the tape into the housing after used. In addition, the conventional tape measure includes a brake device which is used to fix the tape at a certain length for facilitating the measuring operation. When the brake device is released, the tape is automatically retracted into the housing and wound on the reel by the elastic force of the coil spring.
According to the above arrangements, the brake device of the conventional tape measure only provides one-stage tape-fixing function and the tape cannot be simultaneously fixed as the tape is pulled and reaches a desired position. Instead, the tape must be fixed by additionally pushing the brake device. This is troublesome to the user during the measuring operation. Moreover, according to the above one-stage brake device, the tape is likely to unexpectedly automatically retract into the housing due to incautious pulling of the tape and controlling of the brake device. Because the elastically winding force of the coil spring is very large, the user's hands or even body is liable to be hurt by the suddenly retracting tape.
To solve the above problems, U.S. Pat. No. 5,007,178 entitled "measuring tape device" discloses a two-stage brake and control device for the tape, including a first brake mechanism and a second brake mechanism. The first brake mechanism is disposed at a bottom portion of the wound tape, having an actuator lever and an anvil member, wherein a compression spring pushes one end of the lever, making the other end thereof substantially engaged with the anvil member, whereby the tape passing between the lever and the anvil member is substantially fixed after pulled out by a certain length. By means of the elasticity of the compression spring, the tape can be freely pulled out without obstruction. The second brake mechanism is disposed on an oblique lateral side of the wound tape, having a slide button for controlling a slide member disposed inside the wound tape and actuating a force applying member, whereby when pushing the slide button, the force applying member is urged to press and brake or release the tape so as to actually lock the tape at a desired position.
According to the above arrangements of the prior U.S. Pat. No. 5,007,178, the inconveniences in use or operation of the conventional tape measure are eliminated and once pulled out of the housing, the tape is fixed without undesired retraction. Moreover, the slide button serves to actually prevent the tape from suddenly retracting into the housing. Therefore, the above technique achieves the purpose of safe and convenient use of the tape measure. However, a plurality of complicated and room-occupying parts are included in the above structure to achieve the brake function, especially in the second brake mechanism. Accordingly, these parts occupy most of the interior space of the housing and thus the volume and weight of the tape measure are considerably increased. Therefore, it is necessary to improve such structure by reducing the volume and weight of the tape measure and enhancing the operation efficiency thereof.